An unearthly answer to the lightning enigma

By Katia Moskvitch

Now in his 80s, Alexandr Gurevich continues to work full time

Lightning is a natural electrical discharge – but scientists are still scratching their heads trying to figure out what triggers it. Renowned Russian physicist Alexandr Gurevich tells Katia Moskvitch about his theory, which really is out of this world

What don’t we know about lightning?The main problem is that we don’t know how a thundercloud gets the spark needed to initiate a lightning bolt. The biggest mystery is that the electric field in thunderclouds is not very large. Years of experimental measurements from aeroplanes and air balloons have shown that the field is about 10 times smaller than what is needed to initiate lightning. It is not clear how a lightning bolt is born, but the idea is that something has to “seed” it first.

What do we know about how lightning works?In 1749 Benjamin Franklin discovered that lightning was an electrical discharge between a thundercloud and Earth. We know that thunderstorms can generate over 100 million volts of electricity, but we also know that this gets applied across a really large space – hundreds of metres. So the resulting electric field, or concentration of electric force, is not actually very big.

It is estimated that Earth gets struck by more than a hundred lightning bolts every second. How is that electric current released?For lightning to propagate from its point of origin to other locations – the ground, for example – the air, which is normally an insulator, must somehow permit electrical charge to move freely.

The lower part of a thundercloud is negatively charged, and as a storm moves, ...

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